i've been sewing for 45 years---been using niagra starch from the grocery store...for 45 years
have never had it do anything to my iron.
if you want your fabric to have a (crisp) feel---makes cutting much more accurate---give it a spritz.
shake the can well-
spritz lightly (you can always add more if needed) let it soak in a few seconds ---and iron.
it is especially handy when working with homespuns/flannels- will help you have more accurate cuts-
and it washes out when the project is laundered-
just dont store fabrics for any length of time that have been starched- some bugs like the starch---
launderies have been starching our shirts for many many decades---it's nothing to be afraid of.